Preparation of alkali-metal omega-cyanoguanidodithiocarbonates



Patented F eb. 6, 1945 PREPARATION OF ALKALI-METAL w-CY-ANOGUANIDODITHIQCARBONATES RussellqL. Sperry, Stamford, Conn assignor toAmerican. Cyanamjd Company, N. Y., a corporation of Maine New York,

. No viaing.- Application June 7, 1943,

' Serial No.48 9,984

.5 Claims. I 01. 260-500) This invention relates to the preparation -ofalkali metal w-cyanoguanidod-ithiocarbonates.

I have discovered that the alkali metal salts ganic liquids may be usedhowever, such as alpha, beta, gamma-picoline, quinoline,- 2,4-

of t:-cyanoguanidodithiocarbonic acid may be easily and eflicientlyprepared by mixing dicyandiamide, carbon disulfide and an alkali metalhydroxide in the presence of a water miscible, non-hydroxylated organicliquid such as acetone, pyridine or the like. The alkalimetalw-cyanoguanidodithiocarbonates are believed to have the followinggeneral formula:

' MS\ IIIH" n o=N o I -I-oN in which. M is an alkali metal radical. Theformula represents the most probable structure of these compounds andthey are named 'accord ingly. It is quite likely, however, that, thecom,- pounds may exist in whole or in part in one or more tautomericforms, for example:

t t H MSCN--C I I-.CN

Other possible tautomeri'c forms for these com-' pounds could also besuggested and accordingly I do not wish to be bound by the particular,structure set forth. The term alkali metal cyanoguanidodithiocarbonateis intended therefore to include those compounds resulting from thereaction described by me herein regardless of whatever tautomeric formthey may exist in.

The reaction employed by me to, prepare alkali metalw-cyanoguanidodithlocarbonates may be illustrated by the followingequation:

because of the almost quantitative yields obtained when using thesesolvents. Other orin these organic liquids.

lutadiene, methyl-ethyl ke'tone, etc. with less effectiveness.

The reaction is unique 'in that dicyandiamide and the alkali metalhydroxides. are insoluble At the start of the reaction, I have thereforea slurry of dic'yand'iamide and alkali metal hydroxide in, for ex?ample, acetone. As. carbon disulfide is added to this slurry the liquidphase becomes yellow and the 'dioyandiamide particles "are covered witha yellow'material. As the reaction proceeds thev character of the slurrybecomes changed. A voluminous insoluble material micro-crystals ofalkali metal cyanoguanidodi thiocarbonate appears. Upon completion ofthe reaction, the slurry may be filtered and the yellow precipitatewashed' with acetone, alcohol or the like.

The reaction takes place readily over a" wide range of temperatures.The. higher temperatures, above 0., should be avoided since theproduct'has, a tendency to decompose atf'elevated temperatures.'Ordinarily' temperatures ranging from. l0 to65' C. may be employed. Under. thesetemperature conditions the reaction may require from 10 to 1 2hours at -510" Cyto to hour at 60 'C'.- At 15 to 20 0., thereaction isusually complete in l5 minutes' to 1 hour, the time depending somewhatupon the agitation of the reaction mixture, the physical condition ofthe dicyandiamide and the alkali metal hydroxide and the quantity of therer" a'c'tants.

My invention will now be illustrated in. greater detail by means of thefollowing examples. It should be understood however, that these'examplesare given for the purpose of illustration and are not to be construed aslimiting my invention to the particular details describedtherein.

Example 1 A slurry of 210 g. (2.5, moles) of dicyandiamide in 1.5 litersof acetone was cooled to 3 C.

in a three-liter, three-necked flask equipped with thermometer, stirrer,and reflux condenser.

The flask was immersed in an ice-water bath to Well above the level ofthe acetone, and the stirrer was set as close to the bottomof the flaskas possible. 330 g. (5.0 moles) of potas slum hydroxide pellets and 200g. (2.65 moles) of carbon disulfide were added with vigorous stirring;.Before long the temperature began to composed of not was filtered,reslurried in a liter of cold ace tone, filtered, washed with acetone,and dried in a vacuum desiccator overnight. product weighed 587 g.,which represented a 99.8% yield of the crude dipotassiumw-cyanoguanidodithiocarbonate. It was a canary yellow, microcrystallineproduct, highly soluble in water. The decomposition temperatureDipotassium w-cyanoguanidothiocarbonate was obtained in yields greaterthan 88%.

Other alkali metal salts of w-cyanoguanidodithiocarbonate may beprepared in like man- The dried varied from 168-l74 0., depending on therate I of heating of the sample.

Example 2 l 21 g. dicyandiamide, g. sodium hydroxide pellets, 19.0 g. ofcarbon disulfide and 250 00.1

acetone were mixed and allowed to react for, one hour at 10 C. Thetemperature of thereaction mixture was then raised to 25 C. and: thereaction continued for one more hour. Disodiumw-cyanoguanidodithiocarbonate was recovered as a pale yellow, stickysolid mass in' fair yields.

I Example 3 21 g. dicyandiamide, 20 g. sodium hydroxide pellets, 19.0'g. of carbon disulfide and 250 cc." acetone and 2 g. water. were mixedat room temperature in a reaction vessel. The temperature of thereaction mixture rose to 33 C. in one-half hour whereupon it was cooledand maintained at 2025 C. for one and one-half hours. Disodiumw-cyanoguanidodithiocarbonate was recovered as before but withbetteryields.

Example 4 I V ner by the use of other alkali metal hydroxides 'forexample, acetic-or hydrochloric acid. Upon acidification, a precipitatebelieved to be 2-thio- 4,6-diamino-1,3,5-thiadiazine .is immediatelyobtained. This precipitate is practically insoluble in cold water,alcohol, acetone and other common solvents, and may be washed therewithto remove unreacted dicyandiamide, alkali metal salts and hydroxides andother impurities. The washed material may then be added to adilutesolution of a desired alkali metal hydroxide in ethyl alcohol. Aprecipitate of the alkali metal w-cyanoguanidodithiocarbonate is formedat once. lhis product may be filtered and washed with alcohol or acetoneand dried.

What I claim is: v e j 1. A method of preparing alkali metalw-cyanoguanidodithiocarbonates which comprises mixing an alkali metalhydroxide, di-- cyandiamide and carbon disulfide in the presence of awater soluble, non-hydroxylated organic liquid.

cyandiamide and carbon disulfidein the pres,-

ence of pyridine. I

4. A method of I preparing dipotassium a:-cyanoguanidodithiocarbonatewhich comprises mixing together dicyandiamide, potassium hy droxide andcarbon disulfide with acetone.

5. A method of preparing disodium w-cyano-

